Effect of particle polydispersity on the irreversible adsorption of fine particles on patterned substrates

We performed extensive Monte Carlo simulations of the irreversible adsorption of polydispersed disks inside the cells of a patterned substrate. The model captures relevant features of the irreversible adsorption of spherical colloidal particles on patterned substrates. The pattern consists of (equal) square cells, where adsorption can take place, centered at the vertices of a square lattice. Two independent, dimensionless parameters are required to control the geometry of the pattern, namely, the cell size and cell-cell distance, measured in terms of the average particle diameter. However, to describe the phase diagram, two additional dimensionless parameters, the minimum and maximum particle radii are also required. We find that the transition between any two adjacent regions of the phase diagram solely depends on the largest and smallest particle sizes, but not on the shape of the distribution function of the radii. We consider size dispersions up-to 20% of the average radius using a physically motivated truncated Gaussian-size distribution, and focus on the regime where adsorbing particles do not interact with those previously adsorbed on neighboring cells to characterize the jammed state structure. The study generalizes previous exact relations on monodisperse particles to account for size dispersion. Due to the presence of the pattern, the coverage shows a non-monotonic dependence on the cell size. The pattern also affects the radius of adsorbed particles, where one observes preferential adsorption of smaller radii particularly at high polydispersity.Comment: 9 pages, 5 figure

Screening effects in flow through rough channels

A surprising similarity is found between the distribution of hydrodynamic stress on the wall of an irregular channel and the distribution of flux from a purely Laplacian field on the same geometry. This finding is a direct outcome from numerical simulations of the Navier-Stokes equations for flow at low Reynolds numbers in two-dimensional channels with rough walls presenting either deterministic or random self-similar geometries. For high Reynolds numbers, when inertial effects become relevant, the distribution of wall stresses on deterministic and random fractal rough channels becomes substantially dependent on the microscopic details of the walls geometry. In addition, we find that, while the permeability of the random channel follows the usual decrease with Reynolds, our results indicate an unexpected permeability increase for the deterministic case, i.e., ``the rougher the better''. We show that this complex behavior is closely related with the presence and relative intensity of recirculation zones in the reentrant regions of the rough channel.Comment: 4 pages, 5 figure

The role of cinema on the tourist destination image formation process

Tourism literature widely acknowledges that images of tourist destinations are a product of all the experiences of an individual, being influenced by a series of information sources. The movies figure amongst this sources, and as an autonomous information agent, which in theory are not associated with the tourist market interests, they transmit information that is perceived as more reliable than conventional publicity. Thus, cinema acts directly on the organic image, creating and perpetuating associations about the places it depicts on the collective imagery. The present article aims to provide a bibliographical state of the art about the influence of films on the tourist destinations’ image, contextualizing the cinema on it’s formation process, as well as the cognitive and phsycological processes involved

Frações da matéria orgânica do solo no cerrado sob sistema agroflorestal no Nordeste do Brasil.

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Eficiência técnica na produção de manga em Petrolina (PE).

Neste estudo será abordada a produção total dos fatores (PTF) na produção de manga no semiárido brasileiro, em específico no Vale do Submédio São Francisco. A maior demanda por produtos agroalimentares de qualidade vem ocasionando mudanças significativas no comportamento da oferta de frutas no mundo inteiro. Neste contexto se encaixa o Vale; entre os produtos cultivados nessa região, a manga se destaca como um dos mais importantes. Em virtude da necessidade de identificar os componente s de eficiência técnica (ET) na produção de manga no Vale do Submédio São Francisco, o artigo tem como objetivo analisar o nível de eficiência técnica dos produtores de manga do Distrito de Irrigação Senador Nilo Coelho em Petrolina (PE). O estudo das variáveis deu-se também por meio da estimação do modelo econométrico paramétrico de função de produção estocástica. O estudo concluiu que apenas sete (7) produtores de setenta e três (73) lotes pesquisados mostraram-se tecnicamente eficientes, dado preocupante, visto que o grau de ineficiência foi de mais de 90%. Em seguida, será apresentado o cronograma de atividades

Effect of glyphosate on the microbial activity of two Brazilian soils.

Glyphosate [N-(phosphonomethyl)-glycine] is a broad-spectrum, non-selective, post-emergence herbicide that is widely used in agricultural. We studied, in vitro, changes in the microbial activity of typical Hapludult and Hapludox Brazilian soils, with and without applied glyphosate. Glyphosate was applied at a rate of 2.16 mg glyphosate kg[-1] of soil and microbial activity was measured by soil respiration (evolution of CO[2]) and fluorescein diacetate (FDA) hydrolysis over a period of 32 days. We found an increase of 10-15% in the CO[2] evolved and a 9-19% increase in FDA hydrolyses in the presence of glyphosate compared with the same type of soil which had never received glyphosate. Soil which had been exposed to glyphosate for several years had the strongest response in microbial activity. Most probable number (MPN) counts showed that after 32 days incubation the number of actinomycetes and fungi had increased while the number of bacteria showed a slight reduction. After the incubation period, high pressure liquid chromatography (HPLC) detected the glyphosate metabolite aminomethyl phosphonic acid (AMPA), indicating glyphosate degradation by soil microorganisms

Maturação de frutos e sementes de pinhão-manso.

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